Telephone system



April 16, 1929. H. w. ULRICH v TELEPHONE SYSTEM 2 Sheets-Sheet Filed July 28, 1927 April 16, 1929; H. w. ULRICH TELEPHONE SYSTEM Filed July 28, 1927 2 Sheets-Sheet Arron/var l UTED STATES HRACE W. ULRICH, 0F NEWARK, NE'W I, intente-oi .einen PATENT OFFICE.

Jnnsiir,`nssienon 'ro BELL TELEPHONE LABRATORIES, INCRPURATED, 0F NEW YRK, N. Y., .A CORPORATION 0F NEW YRK.

'runner-rotin srs'rnivr.

Application filed July 28,

This invention relates to telephone systems Land incre particularly to such system Wherein low frequency signaling current is einploycd :tor signaling over long rangetoll lines.

In long` range signaling with alternating current, it has been round that aside trein the impedance odered to signaling currents by the long transmission lines themselves, there are also present other sources et impedance which tend to dissipate theactuating currents intended to operate the regular ringing relays. Such sources are,- thedirect current bridge usually employed in such systems for the transmission of supervisory signals, and a shunt including a conde, ser in the voice frequency path which heretofore has been permanently connected in bridge of the regular ringing relay and in series with two oiE the windings ot the repeating coil. y

lit is the object of this invention to iinprove the transmission of signaling currents over lone; transmission lines.

This object is attained in accordance with a feature oit the invention, by the provision ol. a circuit arrangement whereby the usually continuous voice frequency path oli' a long;v range toll switching; 'trunk is maintained normally discontinuous, and rendered continuous for conversation purposes only.

Another feature oit `the invention resides in a circuit arrangement whereby the directeurrent bridge employed tor supervisor purposes is disconnected from the toll switchine` trunk hiring` the passage el ringing current thereorer.

A further feature of the invention is ein# bodied in a circuit ariegegeniont wherein the ringing relay is short-circuited in'oinentarily, to coi/er the'tinie of charging.; a condenser associatcd therewith, thereby preventing surges through the rin ing1 relay andthe 'false operation thereof.

The circuit ar angeinent ei'nbodyingr the first and second mentioned features provides tor the altern ate connection oit the direct current bridgafe and `the Voice frequency conder cr to the toll trunkV so that duringperiods oit i'ingiiigg,` there is present across the trunk only one cl3' these bridge, thereby materially reducing;1 the impedance oiiered to the ring ing); current and increasin9,` the efficiency oit the ringing arrangement. i

lllheinyention will be readily understood troni the following detailed. description inane 1927. Serial No. 268,962.

with reference to the accompanying drawin in which Fig.- l shows a toll cord circuit B adapted to interconnect the toll line indicated at A and the toll switching trunk T; and

Fig. 2 shows the toll` switching trunk 'll in full, its associated operators telephone equipmentindicated at D andthe subscribers telephone setindicated at S.

Assuming a call to hye come in oyer the toll line A and the toll operator having' been signaled in the usual manner, she will proceed to answer the call by insertingv plug' i() et her toll cord circuit B into ack ll of the calling toll line A; Relay 12 thereupon operates over an `obvious sleeve circuit, causing relay 14 to operate in a circuit extending' trein grounded battery, armature and front contact ot relay l2, winding et relay 14, to ground over the back contact and armature of relay l5. `The operation of relay 14: prevents the actuation oi' supervisorylainp 13 at this time.` l r The' toll operator then actuatcs the tallr key 16 to bridge her` telephone set (not shown) across the back end of thepcord circuit in order to converse with the distant toll operator to learn the details of the call. ylfhe circuit `'for the tell operators telephone set entends :from the tip contacts et jacla'.. il and plug 10, tip conductor 17 of the cord circuit B, normally closed contacts et ringing),- hey i8. conductor 19, nornially closed contacts oit splitting key 20, closed tip contacts et. talk key 16, conductor 21, through the operators telephoneset, conductor 22, closed contacts of talk key 16, normally closed contacts oi key 20, conductor 23, normally closed con tacts of ringing key 1S, ring` conductor 9A, ringP contacts of plug l0 and jacl 1l.

Upon learning the nature of the call, the toll operator proceeds to extend the connection by testing for an idle toll switchinizj i this sleeve circuit, marginal relay 29`does not operate, but relay ldoes operate, effect-ing an obvious circuit toV relay 31. Relay 31, in operating, disconnects the busy test lead 32 from the tip ofthe cord circuit and cuts the tip conductor thereof through to the ringing' key 18.

Relayl 33nowk operates in a circuit extending from grounded battery, lower winding of `relay 33, Winding of retard coil 34, normally closed ,contacts of relay 35, lower left-hand Winding of repeating coil 36, ring conductor y37 of trunk'T, ring contacts of jack 26 and plug 25,' 'lower normal contacts of ringing key 18, lower \vinding-ofreta1d coil 38, winding of relay 39, armature and back Contact of relay 29, upper winding of retard Vcoil 38, upper normal contacts of ringing key 18, front contact and armature of relay 31, tip contacts of plug 25z and jack 26, tip conductor 40 of trunk T, upper left-hand Winding of repeating coil' 36,', uppermostarmature and. back contact of rela-y y to ground throughtheupper Winding ofl relay As a consequencev ot theoperation of relay 33, relays 35 and 41V operate. The operating j circuit forV relay 41 extends from grounded battery,r lowermost armature and back contact/'of relay 44, lconductor 43, winding of Vrelay 41, conductor 42, front contact Vand armature of relay l33, to ground. The circuit for relay 35'eXtends from grounded battery, lo-Wermost armature andY normally closed contacts of rela-y 44, conductor 45, lower winding'of relay 35, conductor ,46, to ground over the front Contact and armature Vof relay 33. The operation ofrelay 35 causes battery and ground to be disconnected from the tip and ring conduct-ors of the trunk T, by way of its uppermost and lowermost armatures. I The removal of battery and' ground from the trunk T prevents'relay 39 from opf erating, whereby vthe supervisorylamp 46 is not lighted at this time. Relay 35 also causesk Y relay 65 to operate in4 an` obvious circuit whereupon a short' circuit about relay 60 is prepared at the armature-and contacts of relay 65,7for a purpose to presently appear.

Relay 3 3is held operated by way of the retard coil 34'andfthev make-before-break contacts land lowermost armature .of relay 35, to

ground. y

Relay 41; in operating, establishes a circuit extending from the interrupted battery source (not shown), conductor 47, filament 'ofthe guard and disconnect lamp 48, inner "lower armatrue and back Contact of relay 44,

conductor 68, upper armature and front conl Y disconnect lamp 48 associated operator actuate's anon-loclring talk vkey 50 Aassociated Ywith f'theifplugjend of` Vtrunk T whereupon a circuit is established extending from grounded battery lowermost armature and back contact of relay 44, conductors and 51, lower winding of relay 52, alternate contacts ot key 50, to ground b way of the other talk keys in the group o trunks. ln attracting its inner upper armature, relay 52 locks to ground over the non-locking talk keys. At its other armatures, relay 52 connects the toll operators telephone set at D to the tip and ring of the trunk 'l whereupon the toll operator is informed that the subscriber at station S is desired.

The toll switching o erator, in extending the connection tests jact 55 of the line S in kthe usual manner and, finding it idle, inserts the plug 5G into jack 55. An obvious sleeve circuit is thereupon estalfwlished in which rclay 44 operates. Relay 44, in attracting its lowermost armature, causes relay 52 to restore and disconnect the toll operators telel phone set from the trunk; at its inner lower armature relay 44 opens the circuit for lamp 48 whereupon this lamp is extinguished; at its uppermost armature relay 44 disconnects the busy test lead 57 from the tip of the trunk T and renders the tip conductor thereof continuous; at. its lowermost armature relay 44 also opens the circuit for relay 35 whereupon Vthis relay is restored to normal, connecting the direct current bridge to the trunk and removing the condenser 71. The release of relay 35 completes the short circuit about relay G0, hereinbetore mentioned, and duc to the slow releasing characteristic of relay 65 this short circuit is. momentarily maintained, to cover the period of charging of condenser (i2. lVhen relay 35 releases, battery and ground are connected to the ring and tip conductors respectively of trunk 'l` by way of the windings cf relay 33, winding of relay 34, normal niake-beforc-ln'eak contacts and uppermost armature and bach contact of relay 35. It will be noted that relay in scrics with condenser (i2 is also bridged across the conductors oli trunk T, but its winding is now short-circuited as just described. The charg ing of condenser (i2, caused by the rcassocia- Vtion of battery and ground with thc trunk conductors is efected therefore. over a circuit exclusiye of the winding of relay (i0 and including thc armature and front contact of relay G5 and the inner lower armature und back contact ot relay 35, thereby n'cvcnting relay G0 from experiencing a lin-li and cecting a talse signal.

f In connecting ground and battery through the windings of relay 33 to the tip and ring of the trunk T relay 35 causes the supervisory lamp 46 to be lighted as a ringing signal to the toll opera tor. The lamp 46 is caused to be lighted when relay 39 operates in circuit extending from grounded buttery, lower winding of relay 33, winding of retard coil 34, normally closed contacts of relay 35,

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and ack 26, tip conductor ot trunk T, upper left-hand winding ot repeating coilv 36, uppermost armature and back contact ot relay 35, upper Winding of relay 83, to ground. Relay 39, in operating, established anobvious circuit lor supervisory lainp 46.

Upon noting` the illumination olf lamp 46 at this time, the toll operator realizes that the toll switching trunlr has been connected to the desired subscriber"s line and she proceeds to signal the subscriber by actuating the rin ging lne f Yllzlon the :front end of the cord. The ring;-

ine; relay 66 then operates in a circuit ex terulo ving from the ringing current source 6l associated with the toll opcrators cord, loiver alternate contacts ol key 18, ring;- contacts of plug' 25 and jack 26, ring conductor 37, lower left-hand Winding ol repeatingl coil 36, condenser 62, Winding of relay 60, upper rightliand Winding ot repeating' coil 36, concluetor 40, tip contacts ol' jack 26 and plug V25, armature and front contact of relay 3l, upper alternate contacts ot key 18, to ground. Relay 60, operating in response to theringing current from source 6l, causes relay 66 to operate in series with the upper Winding el relay 35. This circuit is obvious. Relay 35 in operating, disconnects the direct current bridge from the trunk and at its uppermoet 'front contact renders continuous the left-hand side of repeating coil 36 for the transmission ol speech. Relay again operates, as a consequence of the operationoi` relay 35, to ana-in prepare the momentary short circuit for relay 60, as hereinbeitore described.

Relay 66, in operating` as described, connects the ringing current source 67 to ring.

side of the trunk and ground tol the tip, so that the subscriber at S is signaled in a Welllniown manner. Then the ringing lreylS is restored, relay 60 releases, causing relays 66 and 35 to restore, the former disconnectinn,` the rin ging current source 67 liroiu the trunk and the latter completingthe inoinentary short circuit for relay 60 as hereinbelore described and reconnecting the direct current bridge to the trunlrto operate relay 39, and relight lamp 46 at the inwardtoll operators position. l

-When the subscriber responds to the signal by renifrvinn` the receiver freni the switch hook, relay 70 operates ina circuit extending frein grounded battery, Winding. ol relay 70, lower right-hand Winding of repeating coil 36, back Contact and lower armature ott relay 66, ring` contacts of plugr 56 and jack 55 throughthe subscribers telephone set, tip contacts of j ack 55 and plug 56, closed inaliebefore-break contacts ol relay 44, upper arlnature and back contact of relay 66, upper right-hand Winding oi repeating coil 36, to ground. Relay 70, in attracting its armature, causes relay 35 to be operated again over a circuit extending,r from grounded battery, upper Windinskg` olf' relay 35 'front contact and ariuature ol relay 70, conductor 42, to ground on the lront Contact and armature oiI relay 33. Relay 35, in operating at this time, cuts the direct current bridge lroin the trunlc, thereby causing` the supervisory lamp 46 to be eatin- ,ejuished as an iinlieation to the operator that the-called subscriberlias responded. Relay aga-in completes the short circuit about relay 6() to prevent this relay frein 'falsely op'- erating upon the reconnection of the direct current bridge `to the trunk.

The connection is new prepared lor conversation. lt will be noted that at its outer upper armature relay l5 connects the condenser 7l betweenthe tivo left-hand 'windings or repeating coil 36 for the transn'iission ot voice lf'rerpiency currents, but that during the ringing` period relay 35 operated to remove the direct current bridge including battery and grouinltln'ough windings of relay 33 and retard Coil 34.V The reinoval` of this bridge tends to maintain the proper Wave forni of the ringing current inasmuch as its continued association with the trunlr circuit would result in superiinposing direct current on the ringing current and the consequent distortionot the A. C. Wave. 'Subjecting the ringing` relay 6() to superimposed direct current would result in; a less positive operation et the relay. y

At the completionof",v conversation and when the called subscriber at station S replaces the receiver on the switchhoolr, relay 70 releases, causing relay to restore. The

y release .of ,relay` 35 again connects the direct current bridge across the trunlecausing relay 39 to operate,`\vhieh in turn causes the supervisory signal 46 to be actuated as a disconnect signal to the .distant toll operator. Upon noting the illumination of lainp 46 at this time, the dista-nt toll operator removes plug' 25 froni'jaclr 26, whereupon relay 33, which operated upon the connection of the direct current bridge to the trunli, releases, causing relay 41 to restore. Relay 41, upon rcstorjng, opens its own locking` circuit and causes the guard and disconnect signal 48 to llash as a disconnect signal in a circuit extending` frein interrupted battery (not shown), conductor 47, lamp 48, inner lower armature and liront contact of relay 44, to ground at the normal 1nalre-betore-break contacts oi relay 4l.` Uponnoting the flashing ol lamp `48 at ltl time the o nerator removes )lue 56 'troni I Q Jack 55, whereupon relay 44 restores, openlll) ing the circuit for lamp 48 Which is then eittinguislied. The circuit is now in normal condition. y Y Y What isclaimed is: Y l. In a telephone system, a trunk circuit, a .direct current bridge normally connected acrossgsaidV trunk, a condenser, a ringing current source, and means responsive to current from said source for disconnecting said direct current bridge from said trunk and substituting therefor saidcondenser.

2. In a telephone system, ka trunk circuit, a direct currentbridge normally connected across said trunk, av normally open voice frequency path associated with said trunk circuit,`an alternating current relay, and means Y responsivegto theractuation of said relay for disconnecting said bridge from said trunk Vand closing lsaid. voice'requency path.

3. In a telephone system, a trunk circuit, a direct current bridge normally connected across said trunk, a normally open voice frequency path associated with said trunk circuit, an alternating current relay, and a secondrelay controlled by said alternating eurrent relay for disconnecting said direct cur- 4rent bridge from said trunk and closing said voice frequency path.

4. In a telephone system, va trunk circuit,

'a dii'ectwcurrent bridge normally connected lacross saidY trunk, a normally open voice frequencyr path associated With said trunk circuit, an alternating current source, and arelay associatedwith said trunk circuit, said relayY being effective subsequent to the application of current from said source to said trunk for'disassociating said bridge from said y trunkand closing said voice frequency path.

5. -In a telephone system, a trunk circuit having outgoing and incoming ends terminating in arepeating coil forfthe transmission of voice frequency currents,tlie voice frequency path of the outgoing end being nori'nally open, a direct current bridge normally connected to said trunk, a ringing relay responsive to lalternating currentl over said Vvtrunl, and lmeans responsive to the opera Ytrunk and disconnecting tion, of'saidiringing relay for closing the v natiiigin a repeating coil for the transmission of voice frequency currents, the voice frequency path of one eiidvbeing normally open, direct current-.bridge normally connected to said normally open voice frequency `'pat h ,faA relay associated with said trunk, and

a second relay responsive to the actuation of said first relay for closing said-normally y. said direct current bridgetherefromrV r In a vtelephone system, a trunk circuit,

open voice frequencypath and disconnecting a direct current bridge noi-mall connected thereto, a relay in bridge of sait trunk, and means responsive to the actuation of said relay for disconnecting said direct current bridge from said trunk and preparing a short-circuit for said relay, said direct current bridge being connected to said trunk and said short-circuit completed upon the restoration of said means.

8. In a telephone system, a trunk circuit, a direct current bridge normall connected thereto, a relay in bridge of sait trunk, and means responsive to the actuation of said relay for disconnecting said direct current bridge from said trunk and preparing a shortcireuit for said relay, said direct current bridge being connected to said trunk and said short-circuit completed and momentarily maintained upon the restoration of said means.

9. In a telephone system, a trunk circuit, a relay in bridge thereof, a coiu'lenser in the circuit of said relay, means for charging Said condenser, and means responsive to the actuation oif said relay for preparing a short-circuit for said relay, the restoration of said means completing said short-circuit whereupon tlie charge on said condenser is dissipated therethrough.

10. In a telephone system, a trunk circuit, a relay in bridge thereof, a condenser in the circuit of said relay, means for charging said condenser, and means responsive to the actuation of said relay for preparing a short-circuit for said relay, the restoration of said means completing and momentarily maintaining said short-circuit whereby the charge on said condenseris dissipated therethroug i.

1l. In a telephone system, a trunk circuit, a relay in bridge thereof, a condenser in the circuit of said relay, means for charging said condenser, and means inrluding :i slowreleasing relay responsive to the actuation of said first relay for preparing a short-circuit for said lfirst relay, the restoration of said means completing said short-circuit whereupon the charge on said condenser is dissipated. therethrough.

1Q. In a telephone system, a trunk circuit, a relay in bridge thereof, a condenser in the circuit of said relay, means for charging said condenser, and means including a slow-releasing relay responsive to the actuation of said first relay for preparing a short-circuit for said first relay, the restoration of said means completing and momentarily maintaining said short-circuit whereby the charge on said condenser is dissipated therethrough.

13. In a telephone system, a trunk circuit, a relay in bridge thereof, a direct current bridge, means for disconnecting said direct current bridge from said trunk and reconnecting it thereto, and means controlled by said first mentioned means for momentarily sliunting said relay when said direct current bridge is connected to said trunk, thereby preventing surges through said relay.

lei. ln a telephone system, a trunk circuit, a relay in bridge thereof, a direct current bridge, a second relay for disconnecting said direct current bridge from said trunk and reconnecting it thereto, and means controlled by said second relay for momentarily shunting said lirst relay when said direct current bridge is connected to said trunk.

l5. ln a telephone system, a trunk circuit, a relay in bridge thereof, a direct current bridge, a second relay for disconnecting said f direct current bridge from said trunk and reconnorting it thereto, and aslow-releasing relay controlled by said second relay for momentarily sliunting said first relay when said direct current bridge is connected to said trunk.

16. ln telephone system, a trunk circuit, a relay in bridge thereof, and a second relay controlled by said first relay and adapted upon its actuation to prepare a short-circuit for said first relay and upon its restoration to complete said short-circuit.

' 17. In a telephone system, a trunk circuit, a direct current bridge normally connected across said trunk, a condenser, a relay in bridge of said trunlr, means responsive to the actuation of said relay for disconnecting said direct current bridge from said trunlr and substituting therefor said condenser, and means controlled by said first mentioned means for preparing a short-circuit for said relay, said short-circuit being completed when said first mentioned means is restored to connect said direct current bridge to said trunk.

18. ln a telephone system, a trunk circuit, a ldirect current bridge normally connected across `said trunk, a condenser, a relay in bridge of said trunk, means responsive to the actuation of said relay for disconnecting said direct current bridge from said trunlr and substituting therefor said condenser and lmeans controlled by said first mentioned means for preparing a short-circuit for said relay, said short-circuit being completed and momentarily maintained when said first mentioned means is restored to connect said direct current bridge to said trunk.

19. ln a telephone system, a trunk circuit, a direct current bridge normally connected across said trunk, condenser, a relay in bridge of said trunk, means responsive to the actuation of said relay for disconnecting said direct current bridge from said trunk and substituting therefor said condenser, and a slowreleasing relay controlled by said iirst mentioned means for preparing a shorten-cuit for said relay, said short-circuit being completed and momentarily maintained when said first mentioned means is restored to connect said direct current bridge to said trunk. In Witness whereof l hereunto subscribe my naine this 27 day of July f1.1). 1927.

HORACE W. ULRICH. 

